Add-on “appears to be corrupt” when trying to install my add-on's .xpi file in Firefox

Question

I am trying to install an extension in Firefox 45 (same happens with Firefox 49), but Firefox does not allow me to do that, indicating that

Answer 1

Like stated in other answer it happens for unverified/unsigned extension.

But sometimes for testing you might want to use unverified/unsigned extension. As a hack/workaround to install unverified/unsigned extensions following worked for me on Firefox version 45:

1. Launch Firefox and hit - about:config
2. Search for 'xpinstall.signatures.required'
3. Either double click on the row OR set the value to false and close

Now retry installing the extension and it should work.